Thực hiện phép tính:                  a) -1/4 + (-7/8)                           b) 9 (-1/3)^2 + 1/2

   a) \(\frac{{ - 1}}{4} + \frac{{ - 7}}{8} = \frac{{ - 2}}{8} + \frac{{ - 7}}{8}\)                        \( = \frac{{ - 9}}{8}\)                         

b. \(9.{\left( {\frac{{ - 1}}{3}} \right)^2} + \frac{1}{2} = 9.\frac{1}{9} + \frac{1}{2}\)    

                         \( = 1 + \frac{1}{2} = 1\frac{1}{2}\).